I’ve got some 4s lipos chilling in a box hooked up to an led “lipo killer”
It’s been 2 weeks and that light is still on lol. Starting to think it was meant for smaller batteries like for quadcopters.
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Probably not a great idea without knowing exactly how it’s generating load. Purely resistive, sure it could work. But without looking at a schematic it’s all guess work.
Higher end load generators will have load balancing between multiple units, but that’s way beyond a $50 units features.
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I think it’s using the linear region thing in a mosfet. And it’s $25, but it should at least have overcurrent protection (I think).
Hairdryers take a lot of power. Best thing I found around the house.
I haven’t looked into it but nichrome wire maybe would be ideal. If it has high enough resistance and doesn’t transfer heat to the cell
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I didn’t but the other one was at 75% so I assume they were both somewhere near there.
I have 6 others that I shall check later on.
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Ahh. Poor man’s load balancing. Hah.
I’m kidding. Mostly. Please don’t set anything on fire.
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I found schematics.
https://www.eevblog.com/forum/repair/part-identification-150w-constant-current-electronic-load-60v-10a/?action=dlattach;attach=378940;PHPSESSID=0qchk46haqpvb7bk1ub5fanfk1 from https://www.eevblog.com/forum/repair/part-identification-150w-constant-current-electronic-load-60v-10a/
It appears to be some kind of electronic device.
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For sure leaving batteries laying round at full charge is detrimental
They recently changed the voltage cells should be at when shipped a bit lower. Slightly related
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Are you a fuckin wizard? Last thing I expected to just be available online. Haha
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Nowadays all the cool shit seems to be open source or derived, or some nerd reverse engineered it. Great times.
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Okay, I know almost nothing, but I’ve pieced some non-facts together from various youtube videos and some circuits courses from decades ago.
schematics have IRFP250N
https://www.infineon.com/cms/en/product/power/mosfet/12v-300v-n-channel-power-mosfet/irfp250n/
Ptot max 214.0 W
So yeah I think it’s what I said before.
I’m ignoring everything else in the schematic because I don’t understand it so it’s invisible to me lol.
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No doubt. Great time to be of the learning inclination.
Looking at that schematic, it’s actually more advanced than I’d given it credit for.
At a glance it doesn’t look like you’ll blow anything up by using two in parallel but it’s definitely not designed for that. There is reverse current protection built into the input and before the shunt.
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Oh sweet, you’re awesome man. This is worth ordering 2 more I guess, so if I blow 2 up I’ll still have 1.
2 units will let me get to 20A, which is what 30Qs can do, so nice.
Thanks again @DerelictRobot for taking the time to look at the schematics.
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What I would recommend is start each one at below 50% of their maximum and step up the load in unison best you can beyond 50%.
What you want to avoid is one getting overloaded before the other is on if they both turn on at the same time with a max preset load.
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I’d be really interested in the results if you end up carrying this out. Maybe a dedicated thread?
For clarification… are you running these tests from a single 30Q? Will you be trying different specs of nickel strip with accompanying temperature reading during discharge? Sounds like a fun project
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Sooo, yeah, if I get around to doing anything I’ll start a thread. The thing I really want to nail down is, can .15mm or .20mm 10mm wide nickel that spans no more than 2 cell widths handle 20A for more than .5sec?
I’d prefer using a lab power supply to test, but I watched eevblog dave say the BK Precision electronic load is a notorious power supply killer. Whatever pwm or whatnot that these mosfet based loads use to control power is probably not nice to power supplies. I don’t want to blow up $200 psu to test, but I also don’t want to vent with flame. Maybe outdoors with a single cell…
And yeah thermistor on the nickel strip. I should slave everything for control and capture, but I’ll probably just use something like this (I can’t believe these things are so cheap)
Big “if” though, I’m very lazy.
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I think if it’s a lipo most def 100% discharge to a safer voltage. Lipos will always be affected. I’ve probably killed 5-10 lipos or at least the full capacity is shot to about 70-80% vs full 100%.
If it’s 18650, it’s not as fragile but probably still worth to discharge.
We typically use an electronic load tester to discharge. We use something like this https://www.amazon.com/Rigol-DL3021-Programmable-Electronic-Channel/dp/B074P7MTSS/.
You can use these ones they just take forever https://www.amazon.com/MakerHawk-Electronic-Adjustable-Intelligent-Resistance/dp/B07F3NHHST/ref=redir_mobile_desktop/144-9727574-5177716?encoding=UTF8&psc=1&ref=ppx_yo_mob_b_track_package_o0_img @KfromtheBay
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I’ve thrown (2) 30q in parallel one at 3 and other at 4 volts and barely got warm.
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In my dreams 
Definitely something I’d be interested in if I was selling packs. But $500 is a little steep from the non business side. Guess I’ll have to sell some packs to justify a purchase 
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I’ve got a FLIR I can loan you if you do end up doing this testing